用brew安装opencv时刚开始一直出现错误 Error: Failed to download resource "gcc"，并且虽然往下运行了，但一直卡在下面的最后一行 ==> make BOOT_LDFLAGS=-Wl,-headerpad_max_install_names

~ » brew install opencv                                            
Updating Homebrew...
==> Installing dependencies for opencv: gcc, openblas, python@2, numpy, ilmbase, openexr and tbb
==> Installing opencv dependency: gcc
==> Downloading https://homebrew.bintray.com/bottles/gcc-8.3.0.high_sierra.bottl
#################################                                         46.6%
curl: (18) transfer closed with 46734248 bytes remaining to read
Error: Failed to download resource "gcc"
Download failed: https://homebrew.bintray.com/bottles/gcc-8.3.0.high_sierra.bottle.tar.gz
Warning: Bottle installation failed: building from source.
==> Downloading https://ftp.gnu.org/gnu/gcc/gcc-8.3.0/gcc-8.3.0.tar.xz
Already downloaded: /Users/apple/Library/Caches/Homebrew/downloads/790ecda70af93e36763edcb183a8d4e91e433bee9bad9a60360addae9d8e82be--gcc-8.3.0.tar.xz
==> ../configure --build=x86_64-apple-darwin17.7.0 --prefix=/usr/local/Cellar/gc
==> make BOOT_LDFLAGS=-Wl,-headerpad_max_install_names

不知道怎么就好了的解决过程：

1. 运行 gcc --version 查看本地是否已安装gcc，出现相关信息说明已安装。

2. 想到虽然已经有gcc，但之前运行 brew install opencv 的时候还出现安装gcc的信息，好吧我再单独安装一波gcc，运行 brew install gcc，结果显示已安装不能再装了

3. 那既然你都不能再装了，我再试试运行 brew install opencv，然后就好了！

    另外之前卡在的最后一行，这次成功运行的过程中并没有出现这句话。。